There is a possibility your version of Nero will not be compatible with XP SP2 (if Nero 6 a later version has compatibility issues 5.5 may also), that is something you will have to find out for yourself.

Check out the Nero website for compatibility, you may be able to download a patch.

Check out the MS website and search for SP2 section, see if Nero 5.5 is one of the 200+ programs that may not work or have compatibility issues with SP2.

You could update your Nero to the latest retail version (have to pay though).

There truly is only one way to find out and that is to try it. However there could be other old programs that could have issues with XP SP2. I would suggest you get some image backup software so you can do a full backup of your system so you can return to SP1 if you have too many problems.